Multifractal Properties of an Electrical Network in the Percolation Threshold

We consider a square network formed of random electric resistances to the percolation threshold of bond Pc=0.5. We calculate the distribution of current on the infinite cluster with a constant current and constant tension, using a method of gradient conjugated accelerated by LU decomposition. Then we study the multifractal spectrum of the current distribution. Our numerical results are in agreement with the results in literature. The form of the distribution function is nearly Gaussian with the existence of a long tail in the weak current zone. This study leads us to the following findings: the insufficiency of the multifractality to describe all scales of currents; the distribution of strong currents is well understood and it is multifractal, meanwhile the weak currents stays imperfectly known.We also obtain a part of the spectrum which describes the very weak currents that we assign to the currents scales.We consider a square network formed of random electric resistances to the percolation threshold of bond Pc=0.5. We calculate the distribution of current on the infinite cluster with a constant current and constant tension, using a method of gradient conjugated accelerated by LU decomposition. Then we study the multifractal spectrum of the current distribution. Our numerical results are in agreement with the results in literature. The form of the distribution function is nearly Gaussian with the existence of a long tail in the weak current zone. This study leads us to the following findings: the insufficiency of the multifractality to describe all scales of currents; the distribution of strong currents is well understood and it is multifractal, meanwhile the weak currents stays imperfectly known.We also obtain a part of the spectrum which describes the very weak currents that we assign to the currents scales

Numerical study of the effect of the structural disorder on the electronic properties in disordered solids

During the last few years, it became clear that the characterization of the nature of electron states in disordered systems is one of the fundamental topics in condensed matter physics. Along these lines, our present work consists of the study of the effect of the structural disorder on a wide range of electronic properties (density of electron states, participation ratio of electron states and distribution of energy levels). For this, we generate the structural disorder according to three different models: a model named "Shaken lattice’’, a model simulated by molecular dynamics and the model of the random triangles. Concerning the Hamiltonian model, we use a Tight-Binding model with explicit S-type orbitals for the first two structures and a clean Tight-Binding model for the model of the random triangles. Our results show that electron states are localized or delocalized depending on the type of the structural disorder used to generate a particular topologically disordered system.During the last few years, it became clear that the characterization of the nature of electron states in disordered systems is one of the fundamental topics in condensed matter physics. Along these lines, our present work consists of the study of the effect of the structural disorder on a wide range of electronic properties (density of electron states, participation ratio of electron states and distribution of energy levels). For this, we generate the structural disorder according to three different models: a model named "Shaken lattice’’, a model simulated by molecular dynamics and the model of the random triangles. Concerning the Hamiltonian model, we use a Tight-Binding model with explicit S-type orbitals for the first two structures and a clean Tight-Binding model for the model of the random triangles. Our results show that electron states are localized or delocalized depending on the type of the structural disorder used to generate a particular topologically disordered system

Electronic and electrocatalytic properties of PbTiO3: unveiling the effect of strain and oxygen vacancy

First-principles calculations based on density-functional theory have been used to investigate the effect of biaxial strain and oxygen vacancy on the electronic, photocatalytic, and electrocatalytic properties of PbTiO3 oxide. Our results show that PbTiO3 has a high exciton binding energy and a band gap that can be easily moderated with different strain regimes. From a reactivity viewpoint, the highly exothermic adsorption of hydrogen atoms in both pristine and strained PbTiO3 structures does not make it a potential electrocatalyst for the hydrogen evolution reaction. Fortunately, the presence of oxygen vacancies on the PbTiO3 surface induces moderate adsorption energies, making the reduced PbTiO3 suitable for hydrogen evolution reaction processes

Inhibition of β-carbonic anhydrases from Brucella suis with C-cinnamoyl glycosides incorporating the phenol moiety

A small series of C-glycosides containing the phenol moiety was tested for the inhibition of the β-class carbonic anhydrases (βCAs, EC 4.2.1.1) from Brucella suis. Many compounds showed activities in the micromolar or submicromolar range and excellent selectivity for pathogen CAs over human isozymes. Glycosides incorporating the 3-hydroxyphenyl moiety showed the best inhibition profile, and therefore this functionality represents lead for the development of novel anti-infectives with a new mechanism of action.Laboratorio de Estudio de Compuestos Orgánico

Genome Degradation in Brucella ovis Corresponds with Narrowing of Its Host Range and Tissue Tropism

Brucella ovis is a veterinary pathogen associated with epididymitis in sheep. Despite its genetic similarity to the zoonotic pathogens B. abortus, B. melitensis and B. suis, B. ovis does not cause zoonotic disease. Genomic analysis of the type strain ATCC25840 revealed a high percentage of pseudogenes and increased numbers of transposable elements compared to the zoonotic Brucella species, suggesting that genome degradation has occurred concomitant with narrowing of the host range of B. ovis. The absence of genomic island 2, encoding functions required for lipopolysaccharide biosynthesis, as well as inactivation of genes encoding urease, nutrient uptake and utilization, and outer membrane proteins may be factors contributing to the avirulence of B. ovis for humans. A 26.5 kb region of B. ovis ATCC25840 Chromosome II was absent from all the sequenced human pathogenic Brucella genomes, but was present in all of 17 B. ovis isolates tested and in three B. ceti isolates, suggesting that this DNA region may be of use for differentiating B. ovis from other Brucella spp. This is the first genomic analysis of a non-zoonotic Brucella species. The results suggest that inactivation of genes involved in nutrient acquisition and utilization, cell envelope structure and urease may have played a role in narrowing of the tissue tropism and host range of B. ovis

Full potential calculations and atom in molecule analysis of the bonding properties of perovskites Borides XRh

ab initio calculations were performed for the cubic perovskites Borides XRh3B, (X=Dy, Ho, Er). In this work, we have used the augmented plane-wave plus local orbital method to compute the equilibrium structural parameters and electronic structure of densities of states, as well as for the first time, prediction of the thermo-elastic properties of these crystals are presented. The chemical bonding of these compounds has been investigated by using of topological analyses grounded in the theory of atoms in molecules (AIM). All of the electron density critical points in the unit cell were systematically calculated in order to calculate basins interaction of each atoms and give exact classification of the bonding character

Numerical study of the effect of the structural disorder on the electronic properties in disordered solids.

During the last few years, it became clear that the characterization of the nature of electron states in disordered systems is one of the fundamental topics in condensed matter physics. Along these lines, our present work consists of the study of the effect of the structural disorder on a wide range of electronic properties (density of electron states, participation ratio of electron states and distribution of energy levels). For this, we generate the structural disorder according to three different models: a model named "Shaken lattice’’, a model simulated by molecular dynamics and the model of the random triangles. Concerning the Hamiltonian model, we use a Tight-Binding model with explicit S-type orbitals for the first two structures and a clean Tight-Binding model for the model of the random triangles. Our results show that electron states are localized or delocalized depending on the type of the structural disorder used to generate a particular topologically disordered system. Key-words: structural disorder, random matrices, electronic localization, Shaken lattice, molecular dynamics, random triangles. The characterization of electron wave functions in disordered systems has been one of the main interests of condensed matter physicists. The focus has been particularly for some period of time on the nature o

Local pressures in Zn chalcogenide polymorphs

Using the rich polymorphism of ZnX (X: S, Se, Te) compounds, we show how local pressures can be unequivocally determined from i) first-principles total energy calculations, and ii) atomic volumes derived by means of topological analysis of crystalline electron densities. An analogy between atoms and mechanical resistors is put forward since these local pressures lead to the inverse of the thermodynamic pressure once their respective inverses are added up. Accordingly, we define the atomic-like mechanical conductance as a measure of the atomic volume reduction for energy unit under pressure, and prove that, in agreement with chemical hardness expectations, Zn has lower values than S, Se, and Te in all the polymorphs of the chalcogenide crystal family